This invention relates to the collection and removal of fumes, dust and similar material, from a workplace and particularly, to a duct assembly which is controllably movable.
The collection and removal of unwanted material, such as noxious fumes, dust and the like from workplaces such as factories, laboratories etc., can be obtained by the use of ducting having a collecting valve capable of being positioned adjacent to a source of unwanted material, the ducting connected to an abstraction system. Some of the uses of such removal devices include localized sources of fumes or dust such as welding operations, grinding machines, laboratory operations which can produce fumes from chemical reactions, and surgical operations. Such devices typically comprise a duct assembly having a collecting mouth or inlet at one end, and a connection to an abstraction fan at the other a filter or other purification means may be associated with the device. The duct assembly has some flexibility so that the collecting mouth or inlet can be stationed at any desired position. The assembly usually needs to be periodically repositioned and some form of support arrangement is required to retain the assembly in any given orientation and to permit easy movement and repositioning. Once repositioned the assembly should retain the new orientation and not be subject to undesirable movement. The mouth or inlet is normally movable in any direction in a plane and also movable in and out of such plane.
Various arrangements exist providing an adjustable assembly, including the provision of internal or external jointed frames which support the duct. Various devices such as lifting or position-balancing means, such as springs and other devices can be used, together with frictional means at joints.
Canadian Patent number 973,012 (Nederman) discloses a folding duct assembly having an internal duct support extending substantially the length of the duct. The duct support comprises a jointed arm having spring counterbalances to counter the weight of the duct. The joints of the duct support incorporate friction pads to retain the duct in a desired position. Jointed duct support structures are also shown in U.S. Pat. No. 5,527,217 (Engstrom) and U.S. Pat. No. 4,860,644 (Kohl et al). In the Kohl et al device, the joints incorporate friction pads to restrict their mobility, while the joints in Engstrom are linked to a retainer wire that in turn is held in place by a friction fit.
It is desirable, and in most cases essential, that there is provided means for holding the duct assembly in position during use, while still permitting easy movement to a new position. These conflicting requirements are difficult to satisfy with friction type joints. Wear at the joints will interfere with acceptable operation and regular adjustment will be required. If the support structure or frame is housed within the ducts of the assembly, such adjustment becomes very difficult. Also, the action of the friction joints can be adversely affected by the material being extracted through the ducts.
U.S. Pat. No. 6,322,618 to the present inventors discloses an articulated duct arrangement having an external support, including a counterbalance and a gas spring for maintaining the duct in a position set by a user. This arrangement minimizes or replaces the use of friction fittings.
It is desirable to provide a system similar to that previously disclosed by the present inventors, but with various improvements to enhance ease of use and longevity.
An object of the invention is to provide a duct assembly positionable within a wide range, while holding a position, within a range of motion, without the need for friction fittings.
A further object of the invention is to provide improved duct assembly in which at least one duct segment is maintained in a position set by the user, by a means of a spring, preferrably a gas spring, associated with force reversal means to reverse the expansionary force of the spring into a contracting or pulling force, to counteract the force of gravity acting on the duct segments. A further object is to combine such a system, including a retractive force applying means, with a counterbalance arm to counteract the force of gravity acting on a second duct segment joined to the first segment.
The invention provides a ducting assembly which is preferably for collection and removal of material, although not limited to this application. The assembly comprises a plurality of flexibly joined duct sections and a duct support.
The invention comprises an adjustable duct assembly comprising: a base for mounting on a ceiling, wall or other fixed position and first and second elongate duct sections in end to end communicating relation. The first section is flexibly or pivotally joined to the base at a shoulder joint capable of a pivotal swinging rotation (first axis) preferrably also rotation about the axis of the duct (second axis). The first and second sections are flexibly or pivotally joined at an elbow joint. The base, first duct section and second section are joined in a manner in which permits rotation similar to that of a human arm. Namely, the shoulder joint preferrably permits rotation about two axes, while the elbow joint permits rotation about a single axis to permit a folding motion of the duct sections. It will be seen that the shoulder joint may also permit rotation about only a single axis to provide for a folding motion; however it is desirable to also provide for rotation of the duct assembly along its elongate axis at the shoulder joint. An external framework joins together the base and duct sections to permit rotation of the shoulder and elbow joints. Preferably the external framework joining the base with the first duct section, and the framework joining the first and second sections together, is aligned such that a folding motion of the assembly is provided, on a single vertical plane. A counterweight is joined to the second duct section for counterbalancing the rotation of the second section. Retractive force-applying means connect the base and first section to counteract the force of gravity acting on the assembly.
The retraction means include a spring means (i.e. an air spring, coil spring or other like means) for exerting a spreading, i.e. expansionary force tending to urge the ends of the spring apart, mounted to the external framework generally parallel to one of the duct sections. Force reversal means are provided for reversing the normal direction of force of the spring means. The force reversal means comprises first and second links extending around the spring means for converting the normal expansionary force thereof into a retractive force. A first of the links is pivotally mounted to the base and the second link is pivotally mounted to the first duct section, preferrably at a position at or adjacent to an end opposed to the base. Thus, each duct section is linked directly to an end of the gas opposed to the duct section. Preferably, the spring means is a gas spring, and more preferably dual gas springs.
The counterweight may comprise a counterbalance arm mounted to an arm support fixedly mounted to said second duct section.
The first end of the retraction means (or retractor) is preferably supported in a position generally parallel to and displaced from the adjacent first (proximal) duct section. This positioning increases the leverage which may be applied by the retractor. For example, one end of the retractor may be mounted to a scissors-like truss which positions the mount adjacent to the axis of rotation of the shoulder joint, but spaced apart therefrom. The truss comprises first and second arms pivotally jointed together, said first arm being pivotally mounted to the base and the second arm being pivotally mounted to the first external duct support.
A second mount at the opposed end of the retractor may be provided on an arm extending from the opposed end of the same (proximal) duct section.
The counterweight and retraction means are preferably arranged to maintain the duct in a selected position without the aid of a friction joint, within a range of the first duct section being positionable between a substantially vertical position and about 45 degrees below the horizontal, and the second duct section being rotatable about substantially a 360 degree arc relative to the first duct section.
Various connection means may be provided to link the duct sections, and the duct support, for example flexible duct sections. The distal end of the ducts should terminate in a hood or cowling. The system may include a universal flexible section connecting the hood and the first (distal) duct section, for rotational and pivotal movement of said hood relative to said first duct section.